fifo_buffer: added buffering library

It is a library which I have written years ago for other projects.
This library is licensed under BSD 2-clause, because it is very
generic.

1 files changed, 128 insertions, 0 deletions

diff --git a/src/fifo_buffer.h b/src/fifo_buffer.h
new file mode 100644
index 000000000..4af6bde3b
--- /dev/null
+++ b/src/fifo_buffer.h
@@ -0,0 +1,128 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/** \file
+ *
+ * This is a general purpose FIFO buffer library.  You may append data
+ * at the end, while another instance reads data from the beginning.
+ * It is optimized for zero-copy usage: you get pointers to the real
+ * buffer, where you may operate on.
+ *
+ * This library is not thread safe.
+ */
+
+#ifndef MPD_FIFO_BUFFER_H
+#define MPD_FIFO_BUFFER_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+struct fifo_buffer;
+
+/**
+ * Creates a new #fifo_buffer object.  Free this object with
+ * fifo_buffer_free().
+ *
+ * @param size the size of the buffer in bytes
+ * @return the new #fifo_buffer object
+ */
+struct fifo_buffer *
+fifo_buffer_new(size_t size);
+
+/**
+ * Frees the resources consumed by this #fifo_buffer object.
+ */
+void
+fifo_buffer_free(struct fifo_buffer *buffer);
+
+/**
+ * Clears all data currently in this #fifo_buffer object.  This does
+ * not overwrite the actuall buffer; it just resets the internal
+ * pointers.
+ */
+void
+fifo_buffer_clear(struct fifo_buffer *buffer);
+
+/**
+ * Reads from the beginning of the buffer.  To remove consumed data
+ * from the buffer, call fifo_buffer_consume().
+ *
+ * @param buffer the #fifo_buffer object
+ * @param length_r the maximum amount to read is returned here
+ * @return a pointer to the beginning of the buffer, or NULL if the
+ * buffer is empty
+ */
+const void *
+fifo_buffer_read(const struct fifo_buffer *buffer, size_t *length_r);
+
+/**
+ * Marks data at the beginning of the buffer as "consumed".
+ *
+ * @param buffer the #fifo_buffer object
+ * @param length the number of bytes which were consumed
+ */
+void
+fifo_buffer_consume(struct fifo_buffer *buffer, size_t length);
+
+/**
+ * Prepares writing to the buffer.  This returns a buffer which you
+ * can write to.  To commit the write operation, call
+ * fifo_buffer_append().
+ *
+ * @param buffer the #fifo_buffer object
+ * @param max_length_r the maximum amount to write is returned here
+ * @return a pointer to the end of the buffer, or NULL if the buffer
+ * is already full
+ */
+void *
+fifo_buffer_write(struct fifo_buffer *buffer, size_t *max_length_r);
+
+/**
+ * Commits the write operation initiated by fifo_buffer_write().
+ *
+ * @param buffer the #fifo_buffer object
+ * @param length the number of bytes which were written
+ */
+void
+fifo_buffer_append(struct fifo_buffer *buffer, size_t length);
+
+/**
+ * Checks if the buffer is empty.
+ */
+bool
+fifo_buffer_is_empty(struct fifo_buffer *buffer);
+
+/**
+ * Checks if the buffer is full.
+ */
+bool
+fifo_buffer_is_full(struct fifo_buffer *buffer);
+
+#endif